RocHobby Critical Mass: Landing Gear Rake Mod

Like many of us, I absolutely love my RocHobby Critical Mass 1100mm. I thought I'd share a quick and easy mod to make this puppy land even more smoothly than it already does.

OVERVIEW:
Essentially you want to increase the forward rake of the landing gear. Bending the retract wire forward is not an option, not just because the CM ships with great looking struts, but also because the angle would now prevent the gear from fully retracting. The trick, then, is to shim the rear part of the retract mount slightly up from its stock position. Because the angle is increased at the base of the retract, only a small degree of shimming will result in a larger degree of movement of the wheels.

One bonus to this mod are that the model can be returned to its stock configuration simply by removing the shim (no glue or cutting into your model's foam or plastic is required with this mod). Another bonus is that the stock retracts and struts will still align perfectly with the stock wheel well position with zero binding, and in fact, the leading edge of your gear doors will now sit snugly flush beneath the trailing edge of the thick "radiator" there at the forward base of your wheel well. More aerodynamic AND easier to land AND cheap/quick. Trifecta!

PROCESS:

1) Unscrew the four screws which hold the retract into its plastic bay mount.
2) Gently pull the retract assembly up and out, and let it hang where it is (there is no need to pull the wires out any further)
3) Measure the length and width of the rear flat plate (where the two screw holes are).
4) Cut a small piece of 1/8" - 3/16" thick soft balsa or ply to fit those measurements to make a "shim plate".
5) Test fit this wood shim plate between the plastic retract plate and the plastic mounting plate in the wing. Trim until everything lines up. You do not need to cut into any foam, so technically this mod can easily be reversed to return the plan into its stock configuration.
6) With the plate aligned, mark the hole positions and drill them out if you are using lite ply. If using soft balsa, a self tapping screw will suffice.
7) Install your shim plate, sandwiching it between the retract plate and the mounting plate. Use the original screws to screw everything back together.
8) Power on the system and retract your servo to test for any binding. If there are, reduce the thickness of the shim plate.
9) Pat yourself on the back
10) Fly the next day and marvel at your awesome skills. Goodbye, noseovers!

Comment

This mod works great and easy to install. I fly from an artificial turf field, this model loves to nose over. Buy a couple of extra props from MotionRC. When taking off I apply back pressure while gradually advancing throttle slowly and releasing back pressure at the same time. If you just gun the throttle it will more than likely nose over. I like the scale looks of the flaps, but rarely use them do to the fact that it increases the chance of a nose over. This aircraft is a blast to fly, you will not be disappointed.